The invention relates to a plug-in coupling comprising a base body, a sealing ring, a locking ring, and an annular body connectable with the base body, in which a pipe end can be locked in position by the locking ring.
European Patent Application No. EP 587,131 describes such a plug-in coupling, which is constructed as a double coupling and comprises a base body and a holding device or locking device for the corresponding ends of the pipes to be connected, which can be inserted into the coupling body. The holding device comprises a locking ring, which has a locking cone on the outside and at least one locking rib on the inside, which can engage with the corresponding pipe end. By means of a union nut, which can be screwed onto the coupling body, an opposite cone can be locked in position using said locking ring. Furthermore, along the interior of the coupling body, a sealing ring is provided, which fits tightly against the exterior surface of the inserted pipe end.
The pipe end must have sufficient rigidity, so that it does not yield toward the interior due to the radial locking force components, which would jeopardize the axial fixation of the pipe end within the plug-in coupling. When the connection is established, care must be taken that the pipe end is inserted far enough into the coupling body, so that the locking ring as well as the sealing ring can perform their function. If the pipe end is incompletely inserted into the plug-in coupling, there is a risk that the connection is either not being made at all or is being made incorrectly. Furthermore, especially in pressure pipes, there is the problem that the pipe end may be partially moved out of the plug-in coupling due to relative movements of the pipe end in relation to the plug-in coupling, so that the required seal and/or axial fixation can no longer be assured.
It is the object of the invention to provide an improved plug-in coupling for connecting pipes with which a connection can be made with at least one pipe end with little effort and high functional reliability.
Another object of the invention is to provide a plug-in coupling which permits functionally suitable handling during mounting.
A further object of the invention is to provide a plug-in coupling which prevents mounting errors in coupling installation.
It is also an object of the invention to provide a plug-in coupling which is equally suitable for pipes of different materials, such as plastic or metal or a composite thereof (composite pipes made of plastic with a metal interlayer).
A still further object of the invention is to provide a plug-in coupling which can provide a secure connection over many years even for comparatively soft materials, particularly polyethylene, for example.
Yet another object of the invention is to provide a plug-in coupling which is especially suitable for plumbing applications, particularly for hot water and cold water installations.
An additional object of the invention is to provide a plug-in coupling which can reliably absorb any changes in the material, especially with respect to dimensions or rigidity, resulting particularly from temperature changes of the flowing medium.
These and other objects of the invention have been achieved by providing a plug-in coupling comprising a base body, a sealing ring, a locking ring, and an annular body which can be connected with the base body, in which a pipe end can be locked into position by the locking ring, wherein the pipe end can be inserted into an axial annular gap between the base body and the annular body, the sealing ring fits tightly against the interior surface of the pipe end, and the annular gap accommodates the locking ring, which fits under initial stress against a locking surface of the annular body and against the exterior surface of the inserted pipe end.
The plug-in coupling according to the invention is characterized by a functionally reliable design and little complexity in production and assembly. The base body, which partly engages with the interior of the pipe end, assures secure radial support of the pipe end, so that the locking forces of the holding means are reliably absorbed and transmitted even under changing operating conditions. An annular body or cap, which radially surrounds the exterior of the pipe end, is coupled together with the base body. The pipe end is locked into position in an annular space between the base body and the cap. The interior surface of the annular body or the cap is preferably conical.
The locking ring, which is coupled on either side in a non-positive and/or a positive fit with both the interior surface of the annular body and the exterior surface of the pipe, is arranged between said interior surface of the annular body and the exterior surface of the pipe end. The sealing element is preferably arranged on the portion of the base body that engages with the pipe end and fits tightly against the interior surface of the pipe end. The locking or holding ring has at least one holding claw each radially on the inside and radially on the outside, which claws are respectively pressed into the exterior surface of the pipe end and into the interior surface of the annular body.
In one specific embodiment of the invention, the locking ring comprises at least one additional integrally formed clamping element, which is used to produce initial stress on the pipe in the mounted state. This improves and/or accelerates claw fixation of the pipe. The cap comprises at least one projection and/or annular collar associated with the locking ring and/or the clamping element to support the clamping element or the locking ring. The clamping element is seated against the annular collar such that the locking ring preferably contacts the corresponding locking surface of the cap under initial stress. When the pipe end is inserted into the plug-in coupling, the locking ring can yield in axial direction against the prestressing force of the clamping element, while the insertion resistance preferably remains essentially unchanged.
After complete insertion of the pipe end, the locking ring is pressed against the especially conical locking surface of the cap or the annular body by means of the clamping element, so that the pipe end is quickly and securely fixed in the plug-in coupling. Manufacturing tolerances of the plug-in coupling, particularly of the annular body and the locking ring, are thus compensated just as reliably as manufacturing tolerances of the pipe end and particularly its outside diameter. There is no risk that the locking ring mounted inside the cap will already be radially deformed to such an extent that the pipe end can be inserted into the plug-in coupling only by overcoming a large insertion resistance. Advantageously, several, preferably three, such elastic clamping elements are provided. They are connected with the locking ring along one of its axial end faces, particularly via short ribs oriented in substantially axial direction, and form an integral unit with the locking ring. The cap or the annular body preferably comprises radially inwardly pointing projections that can engage with the clamping element to produce radial prestressing and reliable claw fixation and bracing with the pipe end, which is inserted into the plug-in coupling.
Advantageously, the cap or the annular body is provided with at least one inspection window, which is designed particularly in the form of a radial port or opening or an at least partially transparent area. This makes it possible to check at any time by visual inspection whether the pipe end is properly inserted into the plug-in coupling, particularly up to a predefined limit stop. This visual inspection is simple to perform either during or after assembly, including after prolonged operation, so that any impending detachment of the connection can be detected at any time and suitably corrected. The cap is preferably made of a completely transparent material; production problems are avoided due to the one-piece design.
Furthermore, the cap can have at least one transparent window for visual inspection. In this case, the entire cap is advantageously made of a transparent material, which is dyed or provided with a coat of paint on the inside of the cap, except for the inspection window or windows. In addition, or as an alternative, in the context of the invention, the cap can have at least one radially continuous opening or port to permit verification from the outside at any time that the pipe end has been fully and properly inserted into the plug-in coupling. In case of improper assembly, the area of the face of the pipe end is not located radially inside the area of the inspection window or said opening, so that an improper connection can be readily detected.
In a further embodiment of the invention, the sealing ring and the base body comprise holding elements, annular grooves or the like that correspond and engage with one another and/or adjoin one another to fix the sealing ring axially on the base body. As a result, as the pipe end is inserted into the plug-in coupling, the sealing ring maintains its predefined position and any unacceptable pushing of the sealing ring into the plug-in coupling or damage to the sealing ring is avoided. The sealing ring advantageously contains at least one sealing bead or a sealing lip, which can be brought into contact with the interior surface of the associated pipe end. In this case the base body is also arranged within the pipe end.
Also within the scope of the invention, the sealing ring can be arranged or embodied in such a way that it can be brought into contact with the exterior surface of the pipe end. In this case, the base body radially surrounds the exterior of the pipe end in the manner of a sleeve. By means of suitable coupling elements, such as locking rings or clamping rings, particularly provided with holding claws, the pipe end is fixed in the plug-in coupling in a non-positive and/or positive fit.
Particularly advantageously, the sealing ring is arranged in an annular groove provided in the exterior surface of the base body. Between the annular groove and the free end of the base body, the base body contains a ring by means of which the sealing ring is secured against any unintended dislodging or shifting as the pipe end is inserted. The ring is a functionally reliable protection against dislodging of the sealing ring, which fits against the interior surface of the pipe end to form a seal when the pipe end is further inserted. Particularly advantageously, the sealing ring is flat, i.e., its radial thickness is substantially smaller than its axial length. The radial wall thickness of the portion of the base body that together with said sealing ring lies inside the pipe end can thus be designed comparatively small, which ultimately results in an optimized inside diameter of the base body and minimizes the reduction of area.
It should be noted that the plug-in coupling according to the invention can form part of a fitting for connecting two or more pipes, e.g., in the form of an elbow, a wall plate or a T-piece. It can also form a component of the housing of a valve, a transition piece between pipes made of different materials, or the like. When constructed as a fitting or a double coupling to connect two or more pipes, the pipe axes can be positioned at any angle in relation to each other. It should also be expressly noted that the plug-in coupling is particularly suitable for pipes made of different materials and/or with different material properties.
Specific embodiments and further refinements of the invention are set forth in the dependent claims as well as in the following detailed description.